What would cause an 8yr old to have extremely violent outbursts ( strangling, threatening to kill, run away, if you go after them, they think its a gam?

Needs help: For one thing he may be watching too much television, but his outbursts need to be treated. Consult a psychologist or psychiatrist for help.

Child psychologist: You need to discuss about this problem with a child psychologist to see what is the underlying problem here-frustration, anger, sadness etc. Don't ignore that as he would be having major issue in the future if this matter is not handled in a correct way.